Radio waves face significant hurdles when penetrating modern architecture. High-efficiency glass, steel frames, and concrete walls act as signal insulators, leading to "dead zones" within large complexes like malls, airports, and office towers. Morten Tolstrup’s guide emphasizes that relying on outdoor macro cells to serve indoor users is often inefficient; the "penetration loss" is too great to support the high data rates required by 3G and 4G (LTE) technologies. A Tri-Generational Approach
For 2015-era 4G, small cells became cost-effective for low-to-medium density. A picocell (20–100 m range, 32–64 users) can be backhauled via Ethernet. The guide recommends hybrid approaches: DAS for uniform coverage + small cells for capacity hotspots. Radio waves face significant hurdles when penetrating modern